Abstract
Functional connectivity (FC) between the subthalamic nucleus (STN) and the sensorimotor cortex is increased in off-medication patients with Parkinson’s disease (PD). However, the status of FC between STN and sensorimotor cortex in on-medication PD patients remains unclear. In this study, resting state functional magnetic resonance imaging was employed on 31 patients with PD under medication and 31 healthy controls. Two-sample t-test was used to study the change in FC pattern of the STN, the FC strength of the bilateral STN was correlated with overall motor symptoms, while unilateral STN was correlated with offside motor symptoms. Both bilateral and right STN showed increased FC with the right sensorimotor cortex, whereas only right STN FC was correlated with left-body rigidity scores in all PD patients. An additional subgroup analysis was performed according to the ratio of mean tremor scores and mean postural instability and gait difficulty (PIGD) scores, only the PIGD subgroup showed the increased FC between right STN and sensorimotor cortex under medication. Increased FC between the STN and the sensorimotor cortex was found, which was related to motor symptom severity in on-medication PD patients. Anti-PD drugs may influence the hyperdirect pathway to alleviate motor symptoms with the more effect on the tremor subtype.
Highlights
Parkinson’s disease (PD) is the second most common progressive neurological degenerative disorder caused by dopamine deficits in the substantia nigra pars compacta (Lees et al, 2009)
The 31 PD patients contained varying motor symptom severity and durations, with 18 of the 31 patients being more affected at the left side of the body in terms of Unified Parkinson’s disease Rating Scale (UPDRS) III
No significant differences in age, sex, education, Mini-Mental State Examination (MMSE), and MOCA were found for the three groups
Summary
Parkinson’s disease (PD) is the second most common progressive neurological degenerative disorder caused by dopamine deficits in the substantia nigra pars compacta (Lees et al, 2009). Increased STN and M1S1 Connectivity clinical benefits in motor symptom improvement than those obtained by stimulating other sites (Volkmann et al, 2004; Odekerken et al, 2013). The STN stimulates the internal segment of the globus pallidus, leading to increased inhibition of the ventrolateral thalamus. The motor activity is increased within the primary somatosensory cortex (S1), primary motor cortex (M1), and premotor cortical area (Weintraub and Zaghloul, 2013). This phenomenon is an indirect pathway that is depressed by dopamine. The indirect pathway is overactive in PD patients, leading to hyperactivity of the STN (Alexander and Crutcher, 1990). The fast hyperdirect feedback loop from supplementary motor area and M1 cortical projections to the STN via glutamatergic neurons needs further investigation (Tewari et al, 2016)
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